[Haggis]

I remember when I started watching Monster, I maybe watched 5 or 6 episodes a week. By the time I got to the end I watched the last 6 episodes in a single evening. That's what a good ending is all about, you're keen to see how it all gets resolved, it's what the series had been building up to.

I also think it's good if there are questions left unanswered. You watch a series like Monster or Evangelion and you're left thinking about it afterwards. People like to continue the series through their own manga, fan-fictions or even their imaginations. Having a sequel that provides explainations or tells you what subsequently happened to all the characters can often spoil it.